The subject matter disclosed herein relates generally to 180° hybrid couplers and dual-linearly polarized antenna feed networks for four-port antennas.
Hybrid couplers (also referred to as “Hybrid junctions”) are four-port circuits that combine two input signals to create two output signals. Generally, the two output signals from a hybrid coupler are approximately equal in amplitude. Hybrid couplers are named according to the phase difference between their two output ports, with 0°, 90°, and 180° hybrid couplers being the most common configurations. Hybrid couplers are used in a wide variety of applications such as, but not limited to, feed networks, balanced mixers, impedance measuring devices, modulators, phase adjusters, tuners, and comparators.
Known 180° hybrid couplers are not without disadvantages. For example, at least some known 180° hybrid couplers are larger than desired, which may increase the size of a host device, limit the number of hybrid couplers used in a host device (e.g., a feed network) and/or with an associated device (e.g., an antenna), limit the number of host devices and/or associated devices that can be arranged in an available space, and/or the like. Moreover, at least some known 180° hybrid couplers are difficult to manufacture, which may increase cost and/or limit utility of such hybrid couplers.
Another disadvantage of at least some known 180° hybrid couplers is a relatively narrow bandwidth. For example, when used within a feed network associated with an antenna, the operational frequency band of at least some known 180° hybrid couplers may be too narrow to enable the antenna to communicate with one or more devices. Moreover, at least some known 180° hybrid couplers may not operate at relatively high frequencies (e.g., frequencies above one Gigahertz and/or the like), which may prevent a host device and/or an associated device from operating at such frequencies.
Feed networks are used to feed radio frequency (RF) energy between an antenna and an associated electronic system that includes a transmitter, a receiver, and/or a transceiver. For example, feed networks may convert RF waves received by an antenna into RF electrical signals and deliver the RF electrical signals to the associated electronic system, and/or vice versa. Known feed networks may include one or more hybrid couplers (and/or other components such as, but not limited to, baluns, delay lines, and/or the like) for controlling the phase of RF energy at the antenna. As discussed above, a hybrid coupler generates two output signals that have approximately equal amplitude and may have a phase difference of 0°, 90°, and/or 180°.
Known feed networks are not without disadvantages. For example, a plurality of antennas is often grouped together in an array. Each antenna includes a dedicated feed network that serves the particular antenna. Accordingly, the antenna array includes a plurality of antenna and feed network pairs. But, there may be a limited amount of space for containing the antenna and feed network pairs, which may limit the number of antennas that can be included within the array. For example, the length, width, and/or a similar dimension (e.g., a diameter and/or the like) of at least some known feed networks may limit the number of antennas that can be arranged in the available space.
Another disadvantage of at least some known feed networks is bandwidth. Specifically, the operational frequency band of at least some known feed networks may be too narrow to enable the associated antenna to communicate with one or more devices. For example, global navigation satellite systems (GNSSs) transmit over multiple frequency bands. Connectivity to multiple frequency bands of multiple satellite systems enables more reliable and more accurate estimation of location and timing for navigation applications compared with connectivity at a single frequency of a single satellite system. The frequency band of at least some known feed networks may be too narrow to enable the associated antenna to communicate with one or more of the different GNSS satellite constellation operating bands. Specifically, at least some known feed networks operate over a relatively narrow frequency band that does not overlap the frequency band of one or more of the different GNSS satellite constellations. The associated antenna therefore cannot communicate with such a GNSS satellite constellation because the feed network does not operate within the frequency band of the GNSS satellite constellation. Moreover, the frequency band of at least some known feed networks may be so narrow that the associated antenna is limited to communicating with a particular GNSS satellite constellation using only portion (i.e., a sub-band) of the frequency band of the GNSS satellite.